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Designation: D 6500 00
Standard Test Method forDiameter of Wool and Other Animal Fibers Using an OpticalFiber Diameter Analyser1
This standard is issued under the fixed designation D 6500; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Instruments based on image analysis have been designed to reduce the level of operator skill
required and to speed up the measurement process while concurrently maintaining acceptable levels
of precision and accuracy. An additional advantage of image analysis instruments is the ability of the
operator to see the measurement points and to audit the process, if required, though this is not carried
out during routine measurement. As with projection microscope measurements, and the Sirolan-
Laserscan, the Optical Fiber Diameter Analyser (OFDA) system covered by this test method provides
a count of readings grouped into diameter classes. Because the fiber snippets are measured
automatically by an optical and image processing system, controls are provided in the image
processing software to minimize the inclusion of multiple measurements on the same fiber and falsediameter readings that arise from non-fiber material.
1. Scope
1.1 This test method covers a procedure that uses an Optical
Fiber Diameter Analyser (OFDA) for the determination of the
average fiber diameter and the fiber diameter variation in wool
and other animal fibers in their various forms.
NOTE 1This test method may also be applied to other fibers having a
round cross section such as some polyamides, polyesters, and glass; it may
also be applied to a limited number of polyacrylics and regenerated
cellulose-type fibers.
NOTE 2In subsequent sections of this test method, the term wool
also signifies other animal fibers where applicable.NOTE 3For fineness specifications of wool, wool top, mohair, mohair
top, alpaca, and cashmere, refer to Specifications D 3991, D 3992,
D 2252, and Test Method D 2816, respectively.
1.2 The OFDA reports average fiber diameter and standard
deviation of fiber diameter in micrometer units (m). The
coefficient of variation of fiber diameter is reported as a
percentage.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D 123 Terminology Relating to Textiles2
D 584 Test Method for Wool Content of Raw Wool
Laboratory Scale2
D 1060 Practice for Core Sampling of Raw Wool in Pack-
ages for Determination of Percentage of Clean Wool Fiber
Present2
D 1776 Practice for Conditioning Textiles for Testing2
D 2130 Test Method for Diameter of Wool and Other
Animal Fibers by Microprojection2
D 2252 Specification for Fineness of Types of Alpaca2
D 2816 Test Method for Cashmere CoarseHair Content in
Cashmere2
D 3510 Test Method for Diameter of Wool and Other
Animal Fibers by Image Analyzer3
D 3991 Specifications for Fineness of Wool or Mohair and
Assignment of Grade4
D 3992 Specifications for Fineness of Wool Top or Mohair
Top and Assignment of Grade4
D 4845 Terminology Relating to Wool4
2.2 Federal Standards:
Official Standards of the United States for Grades of
Wool, Section 31.05
Measurement Method for Determining Grade of Wool, Sec-
tion 31.2045
Official Standards of the United States for Grades of WoolTop, Section 31.16
Measurement Method for Determining Grade of Wool
Top, Section 31.3016
1 This test method is under the jurisdiction of ASTM Committee D13 on Textiles,
and is the direct responsibility of Subcommittee D13.13 on Wool and Wool Felt.
Current edition approved March 10, 2000. Published June 2000.2 Annual Book of ASTM Standards, Vol 07.01.
3 Discontinued. See 1986 Annual Book of ASTM Standards, Vol 07.02.4 Annual Book of ASTM Standards, Vol 07.02.5 Federal Register, Vol 30, No. 161, August 20, 1965, pp. 10829-10833.6 Federal Register, Vol 33, No. 248, December 21, 1968, pp. 19073-19076.
1
Copyright ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
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USDA Grade Standards for Grease Mohair and Mohair
Top7
2.3 IWTO Standards:8
IWTO-8-66 Method of Determining Wool Fiber Diameter
by the Projection Microscope
IWTO-12-93 Measurement of the Mean and Distribution of
Fibre Diameter Using a Sirolan-Laserscan Fibre Diameter
AnalyserIWTO-19-98 Determination of Wool Base and Vegetable
Matter Base of Core Samples of Raw Wool
IWTO-47-98 Measurement of the Mean and Distribution of
Fibre Diameter of Wool Using an Optical Fibre Diameter
Analyser (OFDA)
3. Terminology
3.1 DefinitionsFor definitions of wool and other textile
terms used in this test method, refer to Terminologies D 4845
and D 123.
3.1.1 average fiber diameter,nthe arithmetic mean width
of a group of fibers.
3.1.1.1 DiscussionIn wool and other animal fibers, all
animal fibers, regardless of species, can be measured using the
OFDA to determine average fiber diameter.
3.1.2 grade, nin wool and mohair, a numerical designa-
tion used in classification of fibers in their raw, semi-processed,
and processed forms based on average fiber diameter and
variation of fiber diameter.
3.1.3 snippet,na wool or other animal fiber that has been
cut to a specified length.
4. Summary of Test Method
4.1 This test method describes procedures for sampling
wool in various physical forms, the reduction of the sample to
small test specimens, and measurement of the diameter of a
number of fibers from the test specimens using the OFDA.Snippets comprising a test specimen cut from the various forms
of wool are cleaned where required, conditioned, and spread
uniformly over the surface of a microscope slide. A cover slide
is placed over the specimen and the slide placed on a
microscope stage, that is moved under computer control. The
slide is stepped through the field of view of a low-power
microscope objective. At each step, the video system is
instructed to capture and analyze a fiber image frame. Each
diameter measurement is allocated to a diameter class and, at
the completion of the slide, the class contents are statistically
analysed to produce the mean and standard deviation of the
fiber diameter for the specimen. Full distribution data are also
available in the form of a printed histogram.
5. Significance and Use
5.1 This test method specifies sampling and testing proce-
dures for the measurement of average fiber diameter and
variation in diameter of animal fibers.
5.2 This test method is considered satisfactory for accep-
tance testing of commercial shipments of wool and other
animal fibers in raw and sliver form because current estimates
of between-laboratory precision are acceptable. In cases of
disagreement arising from differences in values reported by
two or more laboratories when using this test method for
acceptance testing, the statistical bias, if any, between the
laboratories should be determined with each comparison beingbased on the testing of specimens randomly drawn from one
sample of material of the type being evaluated. Test Method
D 2130 shall be used as a referee test method.
5.3 This test method may be used for determining compli-
ance with average fiber diameter and diameter variation to
assign grades when determining conformance of shipments to
material specifications given in Specifications D 2252, D 3991,
and D 3992, and Test Method D 2816.
5.4 The procedures for determining mean fiber diameter and
standard deviation of fiber diameter provided in this test
method and in IWTO Method 47-98 are in essential agreement.
6. Apparatus, Materials, and Reagents
6.1 Optical Fiber Diameter Analyser9, consisting of a trans-mission light microscope, fitted with a stage (motor-driven and
controlled by a computer), stroboscopic illumination that is
synchronised with the stage movement, and a CCD camera; an
image acquisition and analysis hardware system; a means for
controlling the interaction between the camera, stage motors
and illumination unit; a data acquisition and processing com-
puter, with optionally, control and reporting software; and, a
video monitor, capable of displaying each image frame in real
time, for audit purposes. See Fig. 1.
6.2 Glass Microscope Slides9, of float glass, sufficiently
robust to withstand repeated handling having dimensions 70 by
70 by 2 mm. Two identical slides are taped together so that one
supports the fiber samples with the other serving as a coverslide. Slides that are scratched on their inside surfaces are
unsuitable as they may lend to erroneous measurements.
6.3 Cleaning and Conditioning Apparatus and Facilities,
suitable for cleaning and drying the subsamples in accordance
with Test Method D 584 and conditioning them as described in
Practice D 1776.
6.4 Apparatus for Snippet Preparation, having either two
parallel cutting edges between 1.8 and 2.0 mm apart (for
example, guillotine9,10 or snippeter11; see Figs. 2 and 3), or a
cutting diameter of between 1.9 and 2.1 mm (for example,
minicore9,12; see Fig. 4). A minicore consists of a cylindrical
sample holder, designed for relatively large samples, in which
a sample is manually packed, then compressed, and a coringhead is driven pneumatically into the sample. The sample is
compacted by a spring-loaded platen. Six or more minicore
tubes with 2-mm diameter tips pass through perforations in the
7 Federal Register, Vol 36, No. 129, July 3, 1971, pp. 12681-12658.8 Available from the International Wool Textile Organization, International Wool
Secretariat, Commercial Development Department, Valley Drive, Ilkley, Yorkshire
LS29, 8PB, England, UK.
9 Available from BSC Electronics Pty, Ltd., 1A Thurso Rd., Myaree, Western
Australia, 6154.10 Available from Symtech Systems and Technology, I-85 and Bryant Rd., PO
Box 2627, Spartanburg, SC 29304.11 Available from CSIRO, Division of Wool Technology, PO Box 21, Belmont,
VIC 3216, Australia.12 Available from the South African Wool Testing Bureau, Gomery Ave.,
Summerstrand, PO Box 1867, Port Elizabeth 6000, South Africa.
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platen when the force supplied by the pneumatic cylinder
exceeds the force from the preloaded spring. At the end of the
stroke, the cutting tips have penetrated to within 0.5 mm of the
base of the sample holder. The sample collected by the
minicore tubes is automatically expelled into a collection
device upon retraction of the coring head.
6.5 Heavy-Duty Sectioning Device13, comprised of a metal
plate with slot and compressing key and equipped with a
propulsion mechanism by which the fiber bundle may be
extruded for sectioning. The instrument is designed to hold a
sliver or top or equivalent bulk of fibers, yarn, or fabric (see
Fig. 1 of Test Method D 2130). Alternatively, this instrument
can be used to generate the snippets.
13 Available from MICO Instruments, 1944 Main St., PO Box 451, Marshfield
Hills, MA 02051-0451.
FIG. 1 The Optical Fiber Diameter Analyser
FIG. 2 Guillotine and Snippeter
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6.6 Safety Razor Blades, single-edge or double-edge (if
used with blade holder).
6.7 Slide Preparer9 capable of uniformly spreading a por-
tion of the cleaned, conditioned snippet sample over the
surface of a clean glass slide at a predetermined, controlleddensity. For the OFDA, the optimum obscured areas, that is,
the ratio of fiber to the total field area, is between 15 and 25 %.
There are different versions of slide preparers (spreaders)
available and it must be ensured that the same slide preparer is
used for both calibration and routine OFDA measurements. See
Fig. 5.
6.8 Box for Compressing Loose Fibers, 300 by 150 by 375
mm deep, inside dimensions, equipped with a floating top that
has 16 randomly spaced holes 20 mm in diameter over its area.
The sample may be firmly compressed by applying pressure on
the top. The top is held in place by two rods extending through
holes in the side of the box and over the top. The coring tube
is thrust through the holes in the top to sample the wool.
6.9 Pressure Coring Tube, 13-mm inside-diameter metal
tube, approximately 760 mm long, reamed and tapped on one
end to hold a sharp 10 or 13-mm cutting tip. The tube is fittedwith a T cross bar about 500 mm long.
6.10 Core Extruder, 6-mm wood dowel or aluminum rod
slightly longer than the coring tube to push the sample from
tube.
6.11 SolventsPetroleum spirit (boiling range 40 to 70C)
and 1,1,1, trichloroethane. When the preparation method calls
for the cleaning of sliver subsamples, one of these two solvents
shall be used. WarningBoth solvents have associated haz-
ards in terms of volatility, toxicity, and, in the case of
petroleum spirit, flammability. In both cases, care should be
taken in storage, handling, use, and disposal in accordance with
FIG. 3 Guillotine
FIG. 4 Minicoring Device
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the appropriate safety procedures. Refer to manufacturers
material safety data sheets (MSDS).
6.12 Calibration StandardsUsed for instrument calibra-
tion. For wool, use current Interwoollabs IH Standard Tops14
and for mohair, use current International Mohair Association
Standard Tops15.
7. Sampling
7.1 Loose FibersThe method of obtaining a representa-tive sample of wool differs according to circumstances. The
sampling procedures and major circumstances encountered are
as follows:
7.1.1 Lots of Packaged, Grease, Pulled, or Scoured Wool
Take core samples as directed in Practice D 1060. Clean or
scour the raw wool sample as directed in Test Method D 584.
If a representative portion of the scoured wool core sample
resulting from the test for clean wool fiber present is available,
it may be used for fiber diameter determination. If core
sampling is not feasible, take at random, by hand, at least 50
handfuls of wool from not less than 10 % of the packages. The
aggregate mass of the sample shall be at least 1.5 kg.
7.1.2 Major SortFor packaged grease wool in fleece form
for which a diameter test is needed for only the major sort of
the fleece, hand sample by drawing one or more handfuls of
wool from the major sort portions of at least 50 fleeces taken
at random from the lot. The aggregate mass of the sample shall
be at least 1.5 kg.
7.1.3 Piles of Graded or Sorted WoolSample piles of
graded or sorted wool by taking from random locations in the
pile at least 50 handfuls of wool, the aggregate mass of which
shall be at least 1.5 kg. If the wool is in fleece form and a test
is needed for only the major sort, take the sample as directed in
7.1.2.
14 Available from Interwoollabs Secretariat, Boite 14 Rue de Luxembourg 19/21,
1040 Brussels, Belgium.15 Available from International Mohair Association, Mohair House, 68 The
Grove, Ilkley, West Yorkshire, LS29 9PA, England, UK.
FIG. 5 Slide Spreader
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7.1.4 Card SliverSample the wool card sliver by drawing
10 600-mm lengths at random from the lot, preferably during
the carding operation.
7.1.5 TopSample the top by drawing from each 9000 kg
or fraction thereof, 4 sections of sliver, each of which shall be
at least 1 m in length and taken from different balls of top
selected at random. Take only one ball from any one bale or
carton. For broken top, take an equivalent aggregate length ofsliver at random.
8. Test Samples and Test Specimens, Number and
Preparation
8.1 Test Samples (One from Each Lab Sampling Unit):
8.1.1 Grease Wool, Pulled Wool, Scoured Wool:
8.1.1.1 Sub-CoringRandomly pack the core or hand
sample (see 7.1.1, 7.1.2, and 7.1.3) into a suitable container
(see 6.8) and compress to approximately 14 kPa by loading a
weight of 667 N on the floating top. By means of a 10- or
13-mm tipped pressure coring tube, extract at least 5 cores to
provide a test specimen of at least 20 g of scoured wool. Scour
or otherwise clean the test specimen if it is grease wool or
pulled wool as directed in Test Method D 584.8.1.1.2 Gridding, Core Test ResidueIf the sample com-
prises an adequate amount of scoured wool resulting from core
testing a lot for clean wool fiber present, divide the sample into
40 portions of approximately equal size. From each portion,
draw at random at least 0.5 g. Mix or blend these 40 portions
to form the test specimen.
8.1.1.3 Gridding and Machine BlendingFor samples
other than those specified in 8.1.1.1 and 8.1.1.2, divide the
sample into 40 portions of approximately equal size. From
each portion draw at random a sufficient quantity of fiber to
provide a clean test specimen of 20 g. Scour or otherwise clean
the test specimen of grease or pulled wool.
8.1.2 Card SliverStrip off portions of each of the 10600-mm lengths of sliver (see 7.1.4). Combine these portions
to form a composite sliver about 600 mm in length. This
constitutes the test specimen.
8.1.3 TopEach of the 4 sections of sliver comprising the
sample (see 7.1.5) constitutes a test specimen.
8.2 Test Specimens:
8.2.1 Test 1 test specimen from each bulk subsample and 2
specimens from each sliver and top subsample. Prepare ap-
proximately 25-mg test specimens by cutting enough fiber
snippets to measure the diameters of at least 2000 fiber
segments for each test specimen measured. Obtain snippets
using a minicore (8.2.1.1) or guillotine (8.2.1.2). When re-
quired to achieve the necessary quantity of snippets, combinesnippets from one sliver subsample or bulk subsample to form
the test specimen.
8.2.1.1 Minicore (Applicable to Raw Wool, Card Sliver, or
Top)Minicore each sliver subsample or each bulk subsample,
as appropriate, using cutting tips between 1.8 and 2.0 mm in
diameter. If the whole sliver subsample or bulk subsample
cannot fit into the minicore, divide the coring sample into
approximately equal portions of a size to produce at least 2000
individual fiber measurements. Where appropriate, samples of
greasy wool shall be scoured by the procedures outlined in
Practice D 584 before minicoring. Snippets from tops, aqueous
scoured, or carbonized wool should be solvent washed, dried,
and conditioned before measuring.
8.2.1.2 Guillotine (Applicable to Staples, Card Sliver and
Top)Cut snippets from the subsample with a guillotine or
microtome set to a length between 1.8 and 2.0 mm. Make the
same number of cuts from each subsample. Do not cut snippets
within 100 mm of either end of the sliver or make sequential
cuts within the length of the longest fibers.8.2.2 Remove any large pieces of vegetable matter and
excessively long fibers from the test specimens. During re-
moval of large pieces of vegetable matter and excessively long
fibers, handling of the specimen must be kept to a minimum to
avoid preferential separation of fibers of differing diameter.
9. Calibration of OFDA
9.1 A complete calibration and validation of the analyzer
will be necessary following any of the following conditions:
every 3 to 6 months, dependant upon measurement perfor-
mance monitoring; after a change of Interwoollabs standard top
series or a change of International Mohair Association standard
top series; whenever any significant instrument hardware or
software changes or adjustments are made; and, after movingthe instrument.
9.2 Calibration and verification tests for the OFDA are
described in Annex A1.
10. Conditioning
10.1 Condition the cleaned, dried samples for at least 4 h in
the standard atmosphere for testing textiles, 65 6 2 % relativehumidity and 21 6 1C, as directed in Practice D 1776.
NOTE 4Experience to date has involved only sub-sampling and test
specimen preparation from conditioned samples and subsamples. Subse-
quently, it is only necessary to store and measure the test specimens under
standard conditions. Theoretically, it seems reasonable that small amounts
of snippets could be cleaned and dried such that only the test specimen
would need to be conditioned. This approach has not yet been fullyinvestigated and can not, therefore, be recommended.
11. Procedure
11.1 A single operator is sufficient for OFDA testing.
11.2 Pre-Measurement ChecksAt the start of each mea-
surement session, ensure that the instrument is set up according
to the operating manual. Measure at least one test specimen
from a fine top of known diameter and one from a coarse top
of known diameter. During the pre-measurement check, check
the microscope focus and adjust if necessary according to the
operator manual. If at any time during measurement, the
software indicates the microscope is out of focus, manually
adjust the microscope back into focus. If either mean fiberdiameter result varies by more than 0.3 m from the known
value, or from the value determined by at least 10 measure-
ments carried out immediately after calibration of the instru-
ment, check, adjust or recalibrate the instrument until satisfac-
tory performance is obtained.
11.3 Preparation of SubsamplesSee Fig. 6 for the proce-
dure for preparing subsamples from greasy wool cores that
should be used in conjunction with ASTM Test Method D 584.
Fig. 7 is applicable to sliver subsamples.
11.4 Preparation of Snippet SamplesPrepare snippet
samples from subsamples that have been properly cleaned and
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conditioned using minicoring, guillotining, or microtoming.
Obtain enough fiber snippets from each subsample to allow, on
each test specimen, at least 2000 snippet measurements. Table
1 gives the average fiber diameter tolerance ranges obtained
when the procedures and minimum number of acceptable
measurements are made for slivers and greasy wool cores. For
further details on snippet sample preparation, refer to A1.3.1.
11.5 Preparation of the test specimensRefer to A1.3.
Upon completion of the snippet spreading, carefully lower the
clean cover slide over the fibers without disturbing the snippets
and secure in place with a small piece of tape. Prepare only one
slide from each snippet sample. Measure any slides that appear
to be scratched on the inside surfaces without fibers, and, if
readings are observed, discard the slides.
11.6 Measurement of Fiber Diameter DistributionEnsure
that the instrument settings under menu items setup and
calibration are correct and that the optical system and stage
remain clean and free of extraneous fibers. Ensure that the test
specimen slide has no scratches or grease spots and place it
securely in the stage clamps. Measure the whole slide using the
wholeslide31 or wholeslide3 2 options to ensure that atleast 2000 snippets are measured.
11.6.1 Range ChecksCalculate the range checks using the
following:
Range between subsamples5Studentised range*=s2within laboratory(1)
where the sigma squared term is the component of variance
for between subsamples (for example, within laboratory)
calculated from the 1995 round trials conducted under the
auspices of IWTO.
11.6.1.1 Determine the range between 2 slides from the
same subsample. Where this exceeds the value shown in Table1 for the appropriate mean fiber diameter, prepare a new slide.
If the range between 2 of the 3 results falls within the allowable
range, discard the third result. If the range criterion cannot be
satisfied, take a new snippet sample and prepare and measure
2 more slides. If the range between the 2 slides satisfies the
criterion, discard the original measurements. If the range is still
not satisfied, combine all 5 measurements. Calculate the mean
fiber diameter for the subsample.
11.6.1.2 When all the subsamples required (either greasy
cores or sliver) have been measured and the mean fiber
FIG. 6 Preparation of Test Specimens from Core Samples
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diameters calculated for each subsample, calculate the range
between subsamples.
11.6.1.3 In the case of greasy cores, if the appropriate range
for 2 subsamples is exceeded, prepare and measure 2 more
subsamples by scouring and drying 2 greasy core subsamples
from the keeper material. If the appropriate range for 4
subsamples is exceeded, examine the results and determine
whether one of the subsamples can be considered an outlier. If
this is the case, remove that result and determine whether the
range now complies with the appropriate range for 3 sub-
samples. If so, discard the outlier. If the range still cannot
comply, combine the results from all 4 subsamples.
11.6.1.4 In the case of sliver subsamples, if the range
exceeds the appropriate allowable range, test 2 further sub-
samples. If the appropriate range is still exceeded, examine the
results and determine whether one of the subsamples can be
considered an outlier. If this is the case, remove that result and
determine whether the range now complies with the appropri-
ate range for one less subsample. If so, discard the outlier. If
the range still cannot comply, combine the results from all
subsamples.12. Calculation
12.1 For the sample, calculate the average of the mean fiber
diameter, standard deviation and the coefficient of variation
from the results on each slide.
13. Report
13.1 State that the specimens were tested as directed in
ASTM Test Method D 6500 and state the type and number of
samples taken and the kind of material that was tested.
13.2 Report the following information:
FIG. 7 Preparation of Test Specimens from Sliver Samples
TABLE 1 Average Fiber Diameter Tolerance Ranges for VariousNumbers of Subsamples from Slivers and Greasy Cores
Mean Fiber Diameter, m
Sliver Greasy Wool Cores
Less than
26.0
26.0 or
more
Less than
26.0
26.0 or
more
Range Between Two Slides, m 0.4 0.7 0.5 0.9
Range Among Subsamples, m:
Number of Subsamples:
2 0.3 0.5 0.4 0.7
3 0.3 0.6 0.4 0.8
4 0.3 0.6 0.5 0.9
5 0.4 0.6
6 0.4 0.7
7 0.4 0.7
8 0.4 0.7
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13.2.1 The average fiber diameter, m, to one decimal place,
13.2.2 The number of accepted counts (individual measure-
ments made on fiber snippets),
13.2.3 The standard deviation of fiber diameter, m, to one
decimal place,
13.2.4 The coefficient of variation of fiber diameter, to the
nearest whole number,
13.2.5 Optionally, the distribution of fiber diameter as afrequency table or histogram with data grouped into appropri-
ate classes,
13.2.6 Optionally, the 95 % confidence limits for the sample
mean.
14. Precision and Bias
14.1 PrecisionAn international interlaboratory study was
conducted in 1995 under the auspices of IWTO. This led to the
acceptance of IWTO-47 in 1995. In Part I of the study, 40
greasy core samples were selected to cover broad ranges of
average fiber diameter, vegetable matter base, and wool type.
Each sample was supplied to the 4 participating laboratories as
2 150-g subsamples for scouring using the procedures defined
in IWTO-19. Thus, each lab was required to test 80 individual
subsamples using OFDA (also Laserscan and airflow). Each
subsample was tested twice with at least 2000 fibers measured
on every slide (that is, a total of 4 slides and greater than 8000
fibers measured per sample). In Part 2 of the study, 30
Interwoollabs IH Standard Tops were selected to cover a broad
range of average fiber diameter. For all tops, airflow mean fiber
diameter and projection microscope mean fiber diameters and
standard deviations were known. Each sample was supplied to
11 participating laboratories in duplicate, coded to represent
different samples. Each coded sample was measured only one
time with at least 2000 fibers being measured on each slide.
14.1.1 Estimates of the components of variance and the
95 % confidence limits for wool tops and greasy wool cores areshown in Table 2. Table 3 provides the 95 % confidence limits
in 5-m increments for guillotined tops and aqueous scoured
core samples. Similar information for other animal fibers
(mohair, alpaca, cashmere) is being generated by members of
ASTM Subcommittee D13.13.
14.2 BiasThe procedure described in this test method
produces values of average fiber diameter that are not different
than those produced when the same samples are measured by
microprojection (see Test Method D 2130). Hence, this test
method is considered to have no bias for the measurement of
average fiber diameter of wool. In contrast, OFDA measures of
standard deviation tend to be greater than microprojector
measurements, hence the test method is biased in terms ofmeasurements of standard deviation compared to the referee
method.
15. Keywords
15.1 animal fibers (except wool); diameter; diameter distri-
bution; wool
ANNEX
(Mandatory Information)
A1. CALIBRATION OF THE OFDA
A1.1 PrincipleThe OFDA is calibrated for measuring
wool snippets using test specimens prepared from all eight of
the current Interwoollabs IH Standard Tops that have known
mean fiber diameters as determined in round trials using
projection microscopes (a similar set of mohair tops is also
available). The eight mean values obtained from OFDA mea-
surements are converted to non-dimensional W numbers,
that are linearly regressed against the average mean fiber
diameter values supplied by Interwoollabs, so as to allow
determination of the coefficients A and B in the following
equation:
IHmean 5A1B ~OFDAW! (A1.1)
where:
TABLE 2 Components of Variance and the 95 % ConfidenceLimits for OFDA Measurements
NOTE 1The 95 % confidence limits in Table 2 were calculated as
follows: 95 % confidence limits 5 1.96
=s2 within laboratory1 s2 between laboratory.
Type of Sample and
Fiber Diameter
Range
VarianceBetween
Laboratories,m2
VarianceWithin
Laboratory,m2
Variance
Total, m2
95 %
Confidence
Limit, m,6
Guillotined Tops,
17.137.4 m
0.0484 0.0354 0.0838 0.53
Aqueous ScouredCore
Samples,16.039.0m
0.0443 0.0380 0.0823 0.51
TABLE 3 95 % Confidence Limits for OFDA Measurements in5-m Increments
Mean Fiber Diameter, m
OFDA 95 % Confidence Limits, m, 6
Guillotined Tops Aqueous Scoured Core
Samples
15.0 0.18 0.25
20.0 0.30 0.3725.0 0.42 0.48
30.0 0.54 0.60
35.0 0.66 0.70
40.0 0.78 0.82
45.0 0.90 0.92
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IHmean 5 average mean fiber diameter value fromInterwoollabs projection microscope inter-
laboratory trials, andOFDA W 5 non-dimensional fiber diameter number gen-
erated by the OFDA.
This equation is used to calculate the calibration table that
allows the individual OFDA fiber measurements to be assigned
to classes of 1 m width.
A1.2 Calibration Considerations:
A1.2.1 When a calibration is being established for measure-
ment of greasy core samples, the calibration shall be estab-
lished by cutting the calibration tops into 12- to 15-mm
lengths, that shall then be scoured and dried using the proce-
dures outlines in Test Method D 584. The scoured tops are then
brought to equilibrium with the standard atmosphere from the
dry side and subsequently minicored.
A1.2.2 A calibration being established strictly for measur-
ing snippets guillotined or microtomed directly from condi-
tioned sliver can be used to establish a calibration strictly for
measuring slivers. If the slivers to be routinely measured are
expected to contain more than 1.5 % ethanol extract (or 1.0 %
dichloromethane extract), the slivers shall be cleaned to re-
move greasy compounds using petroleum spirit or 1,1,1
trichloroethane. Solvent extracted sliver shall then be dried and
conditioned prior to cutting snippets. If solvent cleaning is
routinely required on slivers to be measured, it should also be
done on the calibration materials.
A1.3 Calibration Procedure:
A1.3.1 Preparation of Snippet SamplePrepare snippet
samples from subsamples of top that have been brought into
equilibrium with the standard atmosphere from the dry side.
Cut enough fiber snippets from each subsample to allow, on
each test specimen, at least 2000 snippet measurements. Amass of between 15 mg at a mean fiber diameter of 20 m and
25 mg at 35 m is usually sufficient. Two methods may be used
to obtain snippets.
A1.3.1.1 Minicoring (Applicable to Sliver and Raw Wool)
Minicore the subsample, or, where the whole subsample cannot
be accommodated in the minicorer, select a representative
portion of about 10 g mass and minicore this portion. Minicore
the subsample or the selected 10-g portion a sufficient number
of times to provide adequate snippet sample for each sub-
sample.
A1.3.1.2 Guillotining or Microtoming (Applicable Only to
Sliver)Cut snippets from each subsample with a fiber cutting
instrument. Make the same number of cuts from each sub-sample. In the case of sliver, do not cut snippets from within
100 mm of either end of the piece. Cut a sufficient number of
times to provide adequate snippet sample for each subsample.
A1.3.2 Storage of snippetsWhatever method is used to
obtain snippets, they must be collected and, if necessary,
stored, in clean vessels of glass or metal, in order to avoid any
segregation that may result from the effects of static electricity.
Snippet samples must be protected against contamination and
drafts that may cause loss of finer fibers.
A1.3.3 Preparation of the Test Specimen(s)Clean all sur-
faces of each glass slide pair by wiping with a lintless swab
dampened with alcohol. Take care at all times to avoid leaving
fingerprints or other deposits on the glass slides, since this may
lead to focusing difficulties and measurement inaccuracy. Do
not allow alcohol to come into contact with the adhesive
holding the hinge between the pair of slides. Insert a clean
glass slide in the slide preparer and, using a pair of tweezers or
a miniature sampling spoon, select about five equally repre-
sentative portions of the snippet sample and introduce them tothe slide preparer. It is preferable to use the entire snippet
sample, or, where this is not feasible, ensure that snippets are
representatively selected from the entire depth of the sample to
avoid the effects of snippet segregation. Also, ensure that the
entire part of the sample placed in the spreader is allowed to
pass through onto the slide, since in some samples the coarse
fibers fall first through the spreader. Where the snippet samples
have been prepared from a sample containing high levels of
vegetable matter, it may be necessary to remove residual
non-fibrous particles from the snippet samples using a pair of
tweezers in order to avoid focusing problems caused by
inability to fully close the slide pair. Upon completion of the
snippet spreading, carefully place the clean cover slide over the
fibers without disturbing the snippets and secure in place.
Prepare one slide from each snippet sample.
A1.3.3.1 Number of Test SpecimensIn order to maintain
equal precision of the mean for each top, the number of slides
necessary shall be determined by the between-slides variance.
The variance shall be determined by measuring a suitable
number of slides prepared for each top. Calculate the number
of slides,m, in order to achieve a standard error of the mean of
0.1 m. As guidance, for the 10th Interwoollabs IH series
(1994), the following minimum numbers of slides are recom-
mended: 17.0 and 19.1 m2 each; 20.5 and 23.6 m4
each; 27.1 and 29.5 m6 each; 34.3 and 37.7 m8 each.
A1.3.4 Measurement of Fiber Diameter Distribution
Operate the instrument in a clean, substantially dust-freeenvironment maintained at standard atmosphere. Where the
electricity supply is noisy or subject to disturbance, the
equipment supply shall be protected by an uninterruptable
power supply and conditioning unit.
A1.3.4.1 Premeasurement CheckEnsure that the instru-
ment is set up in accordance with the instructions in the
operating manual. Check the microscope focus and adjust if
necessary. If at any time during measurement the software
indicates the microscope is out of focus, manually bring the
microscope back into focus.
A1.3.4.2 Measurement of Calibration SlidesMeasure
each slide with the instrument set on Wholeslide3 1 or
Wholeslide 3 2. In each case, ensure that the total count sizeis at least 2000. Print the mean values. Record the offset andslope for the calibration used in the measurements.
A1.4 Calibration CalculationsThe following calculations
may be conveniently carried out on any spreadsheet program
that allows calculation of linear regression coefficients. The
normal precautions should be taken to ensure that the program
gives the same results as the manual procedure below. Round-
ing should not be carried out.
A1.4.1 Calculation of Means for Each TopFor each of the
m slides prepared, calculate the average mean fiber diameter
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value,difrom the mean fiber diameters reported for each of the
slides,dn:
di 5 ~(n51m
dn!/m (A1.2)
From the OFDA calibration menu, determine the offset and
slope of the current calibration, that may be the factory
calibration. For each top, calculate the mean W value:
Wi 5 ~di current offset!/current slope (A1.3)A1.4.2 Calculation of Coeffcients:
A1.4.2.1 Calculate the following means:
a 5 ~(i518
Wi!/8 (A1.4)
b 5 ~(i518 Fi!/8 (A1.5)
where Fi is the mean fiber diameter value supplied byInterwoollabs for the ith top.
A1.4.2.2 Calculate coefficient B from:
B5(i518 ~Wi a! ~Fi b!
(i518 ~Wi a!
2 (A1.6)
and coefficient A from:
A5 b Ba (A1.7)
On completion of the calibration calculations, select Cali-
bration on the instrument menu and input the new calibration
using the value ofA as the new Offset and the value ofB as
the new Slope.
A1.5 Verification of Calibration:
A1.5.1 PrincipleTest samples of wools with known mean
fiber diameters and distribution characteristics are measured
using the new calibration. Preferably, these are different tops
than those used for calibration. The results are compared to the
known values and the calibration is accepted if the differences
fall within acceptable limits outlined in A1.5.3. If the criteria
are not satisfied, corrective action (that is, recalibration) mustbe taken.
A1.5.2 ProcedureWith the new calibration installed, pre-
pare and measure (using identical sample preparation, cutting,
conditioning, and spreading methods as were used for calibra-
tion) a new set of slides comprising at least 2 from each of 8
tops with known characteristics. More slides may be necessary
for the coarser tops, depending on the level of between-slide
variance. For the mean of each pair of slides, calculate the
difference (Gi) between the measured mean fiber diameter (di)and the known value (Fi).
A1.5.3 CriteriaEach of the following criteria must be
satisfied:
A1.5.3.1 Criterion 1
Calculate the mean,D
, varianceSD
2
,andt-value,t, for the differences using Eq A1.8-A1.10 respec-
tively:
D5 ~(i518 Gi!/8 (A1.8)
SD2 5 $(i51
8 Gi2 @~(i51
8 Gi!2/8#%/7 (A1.9)
t5 ~D= 8!/SD (A1.10)
The t-value must not exceed 2.365, this being the Students
t-value for 7 (that is,n-1) degrees of freedom at the 0.05 level.
A1.5.3.2 Criterion 2Calculate the gradient, g, variance,
Sg2, andt-value for the regression of the differences against the
given Interwoollabs mean fiber diameters using Eq A1.11-
A1.13 respectively:
g58(i518 Gi2 ~(i518 Gi! ~(i518 Fi!
8(i518 Fi2 ~(i518 Fi!2 (A1.11)
Sg2 5U8(i51
8 Gi2 ~(i518 Gi!2
8(i518 Fi2 ~(i518 Fi!2 g2U/6 (A1.12)
t5g/Sg (A1.13)
the t-value must not exceed 2.447, this being the Students
t-value for 6 (that is,n-2) degrees of freedom at the 0.05 level.
A1.5.3.3 Criterion 3To calculate the mean square error of
the calibration, use the mean measured diameters obtained
from the eight sets of verification slides (OFDAi) and the eight
projection microscope values (PM) supplied by Interwoollabs
for the tops (Fi). Calculate the regression between the assignedPM values and the average OFDA values as follows:
U5 (i518
OFDAi!/8 (A1.14)
V5 ~(i518 Fi!/8 (A1.15)
where Fi is the mean fiber diameter value supplied byInterwoollabs for the ith top. Calculate coefficients S and T
using the following equations:
S5V TU (A1.16)
T5(i518 ~OFDAi U! ~Fi V!
(i518 ~OFDAi U!2 (A1.17)
Calculate the equivalent regressed PM values for each top
using the following equation:
PMi 5S1T3OFDAi (A1.18)
Calculate the mean square error as follows:
MSE5(i51
8 ~Fi PM i!2
6 (A1.19)
The MSE must not exceed 0.10 m2.
A1.5.4 VerificationIf any of the criteria cannot be satis-
fied, the instrument may need adjustment, or one of the slides
may not be representative. An anomaly usually may be isolated
by examining plots of the calibration and verification data
against the regression line. The instrument must be recalibrated
if it needs to be adjusted. Immediately after a calibration has
been concluded and verified, it is often convenient to remea-
sure the mean fiber diameter and standard deviation of all or a
selection of the slides used in the calibration (and any othersthat may be considered helpful to cover an extended range of
fiber characteristics), and to record the results on labels affixed
to the slides. Such slides, as long as they are securely taped
around the edges, stored horizontally, kept at the standard
conditions, handled carefully, and kept free from grease or
other surface contamination, may be used for routine premea-
surement checks on the instrument.
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